Corrosion mitigation for gearbox

ABSTRACT

A magnesium component of a rotary wing aircraft is provided including a groove including a first sidewall and a second sidewall arranged on opposing sides of a recessed opening. The first sidewall includes a deposit positioned adjacent the recessed opening. The deposit is formed by cold spraying one or more layers or powdered material within an area of the first sidewall from which material was removed.

BACKGROUND OF THE INVENTION

Exemplary embodiments of the invention relate to components of arotary-wing aircraft susceptible to corrosion damage and, moreparticularly, to a method for preventing or reducing corrosion damage tosuch a component of a rotary-wing aircraft.

A rotary-wing aircraft includes components, such as gearboxes forexample, typically constructed from aluminum and magnesium alloys. As aresult of exposure of such components to the environment, these alloymaterials are susceptible to corrosion. For example, the presence ofwater or moisture on the outer surface of the component may causecorrosion and other environmental conditions, such as chemical falloutand saltwater for example, may exacerbate corrosion. Corrosion causesthe material of the component to deteriorate, thereby reducing the wallthickness thereof In some instances, the component's wall thickness maybe excessively reduced such that the structural integrity of thecomponent is compromised.

Conventional rotary-wing aircraft component repair methods allow fordimensional restoration of aluminum and magnesium structures using avariety of techniques including, but not limited to, epoxy bonding,plasma spray, high velocity oxygen fuel (HVOF) thermal spray and fusionwelding for example. High temperature repair techniques may result inunacceptable component distortion and degrade the substrate materialproperties by over-aging or solutioning. Epoxy bonding can break orspall during service, allowing the environmental elements to attack theunderlying material. Subsequent attacks on the material will deterioratewall thickness such that the component is no longer usable.

BRIEF DESCRIPTION OF THE INVENTION

According to one embodiment of the invention, a magnesium component of arotary wing aircraft is provided including a groove including a firstsidewall and a second sidewall arranged on opposing sides of a recessedopening. The first sidewall includes a deposit positioned adjacent therecessed opening. The deposit is formed by cold spraying one or morelayers of powdered material within an area of the first sidewall fromwhich material was removed.

According to another embodiment of the invention, a method of rebuildinga damaged portion of a groove in a magnesium component is providedincluding forming an area in a sidewall adjacent the recessed opening byremoving all material exhibiting wear or localized corrosion andpitting. A deposit is created in the area and is integrally formed withthe sidewall and an inner surface of a recessed opening of the groove.Excess material is removed as needed, from the deposit.

According to another embodiment of the invention, a method ofpreemptively forming a deposit in a groove of a magnesium component isprovided including removing material from a sidewall adjacent a recessedopening of the groove to form an area. Damage is expected to occur inthe area from which the material is to be removed. A deposit is formedin the area. The deposit is integrally formed with the sidewall and aninner surface of the recessed opening. Excess material is removed asneeded, from the deposit.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter, which is regarded as the invention, is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other features, and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIG. 1 is a perspective view of an exemplary rotary wing aircraft;

FIGS. 2 a and 2 b are exemplary schematic diagrams of the main rotorsystem and the tail rotor system of the aircraft of FIG. 1;

FIG. 3 is a perspective view of a gearbox housing of a rotary wingaircraft according to an embodiment of the invention;

FIG. 4 is a cross-sectional view of a portion of the gearbox housingillustrated in FIG. 3 including a groove;

FIG. 5 is a cross-sectional view of a portion of a gearbox housinghaving an integrally formed deposit according to an embodiment of theinvention;

FIG. 6 is a method for rebuilding a portion of a groove of a gearboxhousing according to an embodiment of the invention; and

FIG. 7 is a method for preemptively forming a deposit in a groove of agearbox housing according to an embodiment of the invention.

The detailed description explains embodiments of the invention, togetherwith advantages and features, by way of example with reference to thedrawings.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 schematically illustrates a rotary-wing aircraft 10 having a mainrotor system 12. The aircraft 10 includes an airframe 14 having anextending tail 16 which mounts a tail rotor system 18, such as ananti-torque system, a translational thrust system, a pusher propeller,or a rotor propulsion system for example. Power is transferred from oneor more engines E to a power transmission gearbox 20 (see FIGS. 2 a and2 b), to drive the main rotor system 12 about a respective axis ofrotation A. Although a particular rotary wing aircraft configuration isillustrated and described in the disclosed embodiment, otherconfigurations and/or machines, such as a high speed compound rotarywing aircraft with supplemental translational thrust systems, a dualcontra-rotating, coaxial rotor system aircraft, and a turbo-prop,tilt-rotor or tilt-wing aircraft for example, will also benefit from thepresent invention.

Referring now to FIG. 2 a, a schematic diagram of the main rotor system12 and the tail rotor system 18 of the aircraft 10 of FIG. 1 is providedin more detail. In the illustrated non-limiting embodiment, the powertransmission gearbox 20 is interposed between one or more engines E, themain rotor system 12 and the tail rotor system 18. The gearbox 20 may bemechanically connected to and configured to operate both the main rotorsystem 12 and the tail rotor system 18, In another embodiment, shown inFIG. 2 b, the rotary wing aircraft 10 includes a. first powertransmission gearbox 20 a. mechanically coupled to and configured tooperate the main rotor system 12. Similarly, a second power transmissiongearbox 20 b is mechanically connected to and configured to operate thetail rotor system 18. Each of the power transmission gearboxes 20 a. 20b receives power from at least one engine E of the aircraft 10.

Each power transmission gearbox 20 is generally mounted within a housing22 (see FIG. 3) configured to support the gear-train therein. In oneembodiment, the gearbox housing 22 includes a magnesium material. In theillustrated, non-limiting embodiment, the housing 22 generally includesa plurality of first openings 24 and a plurality of second openings 26.The plurality of first openings 24 may be configured to provide aplurality of passageways for a lubricant to various portions of thegearbox 20 for example. The plurality of second openings 26 may beconfigured to at least partially support an input module attachment (notshown), such as the rotor shaft (not shown) of the main rotor system 12or the tail rotor system 18 for example. Although a particular gearboxhousing 22 configuration is illustrated and described in the disclosednon-limiting embodiment, other configurations are within the scope ofthe invention.

The gearbox housing 22 additionally includes one or more grooves 30, asillustrated in FIG. 4, having a recessed opening 32 surrounded onopposing sides by a similar first and second sidewall 34. Each groove 30is configured to receive a component, such as an o-ring seal forexample. In one embodiment, the plurality of grooves 30 are arrangedwithin one or more of the plurality of first openings 24 or theplurality of second openings 26, as illustrated in FIG. 4, such that thesidewalls 34 are formed by the housing 22. However, the grooves 30 maybe formed in any portion of the gearbox housing 22.

Portions of the housing 22, in particular the sidewalk 34 of the grooves30 are highly susceptible to wear, as well as to corrosion and/orpitting. Referring now to FIG. 5, a deposit 40, illustrated as a. shadedregion, forms at least a portion of one or more of the sidewalls 34 of agroove 30 in the gearbox housing 22. The deposit 40 may be formed fromany suitable powdered material known in the art. such as aluminum oraluminum alloy for example. In one embodiment, the deposit 40 is formedas a means of repairing the housing 22 after wear or corrosion andpitting has already occurred. In another embodiment, the deposit 40 isformed as a “preemptive repair” based on a determination of where damageto the sidewall 34 is most likely to occur.

Each deposit 40 is formed by applying one or more layers of powderedmaterial to an area 42 of the sidewall 34 adjacent the recessed opening32. In embodiments where the deposit 40 is applied to the housing 22after damage has occurred, the area 42 is formed by removing the damagedmaterial from the sidewall 34. In one embodiment, the material removedto form area 42 extends from the inner surface 38 of the recessedopening 32 to the outer surface 36 of the sidewall 34 and has a depthsufficient to completely eliminate all of the localized damage orcorrosion. Some of the adjacent non-compromised material of the sidewall34 may additionally be removed along with the damaged material to ensurethat the remaining material of the sidewall 34 has not been compromised.In embodiments where the deposit 40 is applied “preemptively,” each area42 is created by removing material from the sidewall 34 where damageand/or corrosion and pitting are most likely to occur.

The layers of powdered material used to form the deposit 40 aregenerally applied through a deposition process that provides sufficientenergy to accelerate the particles to a high enough velocity such thatthe particles plastically deform and bond to the area 42 upon impact.The particles of the powered material are accelerated through aconverging/diverging nozzle 52 of a spray gun 50 to supersonicvelocities using a pressurized or compressed gas, such as helium,nitrogen, other inert gases, or mixtures thereof The deposition processdoes not metallurgically transform the particles from their solid state.Various techniques may be used to achieve this type of particledeposition, including but not limited to, cold spray deposition, kineticmetallization, electromagnetic particle acceleration, modified highvelocity air fuel spraying, or high velocity impact fusion (HVIF) forexample.

The layers of powered material may be applied to the original materialof the housing 22, or alternatively, may be applied to a previouslyformed deposit 40. During deposition of the powdered material, thegearbox housing 22 may be held stationary or may be articulated ortranslated by any suitable means (not shown) known in the art.Alternatively, the nozzle 52 of the spray gun 50 may be held stationaryor may be articulated or translated. In some instances, both the gearboxhousing 22 and the nozzle 52 may be manipulated, either sequentially orsimultaneously.

A method 100 for rebuilding a damaged portion of a groove 30 of agearbox housing 22 is illustrated in FIG. 6. The method begins in block102 by removing all of the localized damage from at least one of thesidewalls 34 of the groove 30 to form an area 42 (see FIG. 5). Thecorrosion and pitting may be removed either mechanically or chemically,for example using grinding, machining, etching, or other applicabletechniques. In block 104, at least one layer of powdered material isapplied to the area 42 using a cold spray deposition process to create adeposit 40 integrally formed with the inner surface 38 of the recessedopening 32 and the remainder of the sidewall 34. When bonded to the area42, the deposit 40 may extend beyond the original dimensions of thesidewall 34 of the gearbox housing 22. After formation of the deposit40, excess material is removed as necessary, as shown in block 106. As aresult, the deposit 40 is generally flush with the remainder of thesidewall 34 of the gearbox housing 22 and/or the dimension of thegearbox housing 22 including the deposit 40 is substantially equal tothe original dimension thereof

A method 200 of preemptively forming a deposit 40 in a sidewall of ahousing 22 is illustrated in FIG. 7. The method 200 begins in block 202by removing some material from the sidewall 34 of an unused gearboxhousing 22, at a position where localized corrosion and pitting is mostlikely to occur, to form an area 42. Material may be removed from thesidewall 34 either mechanically or chemically, for example usinggrinding, machining, etching, or other applicable techniques. In block204, at least one layer of powdered material is applied using a coldspray deposition process to form a deposit 40. The deposit 40 formedwithin the area 42 of the sidewall 34 may extend beyond the originaldimension of the surface 30 of the gearbox housing 22. In suchinstances, excess material is removed after formation of the deposit 40,as shown in block 206. The excess material 40 may be removed so that thedeposit 40 is substantially flush with the remainder of the sidewall 34of the gearbox housing 22 and/or so that the dimension of the gearboxhousing 22 including the deposit 40 is generally equal to the originaldimension thereof

Formation of one or more deposits 40 in the sidewalls 34 of one or moregrooves 30 in a gearbox housing 22 can reduce and/or prevent corrosionand pitting, thereby improving the life of the housing 22. In addition,use of a cold spray deposition process will not affect the heattreatment condition of the magnesium substrate and its materialproperties, a consideration which normally limits the availability ofrepairs of magnesium components.

While the invention has been described in detail in connection with onlya limited number of embodiments, it should be readily understood thatthe invention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of the invention havebeen described, it is to be understood that aspects of the invention mayinclude only some of the described embodiments. Accordingly, theinvention is not to be seen as limited by the foregoing description, butis only limited by the scope of the appended claims.

What is claimed is:
 1. A magnesium component of a rotary wing aircraftcomprising: a groove including a first sidewall and a second sidewallarranged on opposing sides of a recessed opening, wherein the firstsidewall includes a deposit positioned adjacent the recessed opening,the deposit being formed by cold spraying one or more layers of powderedmaterial within an area of the first sidewall from which material hasbeen removed.
 2. The magnesium component according to claim 1, whereinthe magnesium component is a gearbox housing.
 3. The magnesium componentaccording to claim 1, wherein the powdered material includes aluminum.4. The magnesium component according to claim 1, wherein the materialremoved from the sidewall includes at least one of wear, corrosion, andpitting.
 5. The magnesium component according to claim 1, wherein damageis expected to occur to the material removed from the sidewall.
 6. Themagnesium component according to claim 1, wherein the deposit extendsfrom an inner surface of the recessed opening to an outer surface of thesidewall.
 7. The magnesium component according to claim 1, wherein themagnesium component including the deposit has at least one dimensionsubstantially equal to an original dimension of the magnesium component.8. The magnesium component according to claim 7, wherein the deposit issubstantially flush with a remainder of the sidewall.
 9. A method ofrebuilding a damaged portion of a groove in a magnesium component,comprising: forming an area in a sidewall adjacent a recessed opening ofthe groove by removing all material exhibiting wear or localizedcorrosion and pitting; creating a deposit in the area, the deposit beingintegrally formed with the sidewall and an inner surface of a recessedopening of the groove; and removing any excess material from thedeposit.
 10. The method according to claim 9, wherein the magnesiumcomponent is a gearbox housing of a rotary wing aircraft.
 11. The methodaccording to claim 9, wherein the deposit includes one or more layers ofpowdered material applied to the area through a cold spray depositionprocess.
 12. The method according to claim 11, wherein the powderedmaterial includes aluminum.
 13. The method according to claim 9, whereinthe deposit extends from an inner surface of the recessed opening to anouter surface of the sidewall and has a depth configured to completelyeliminate all damage from the sidewall.
 14. The method according toclaim 9, wherein excess material is removed so that the deposit issubstantially flush with an outer surface of sidewall.
 15. The methodaccording to claim 9, wherein excess material is removed so at least onedimension of the magnesium component including the deposit issubstantially equal to an original dimension thereof.
 16. A method ofpreemptively forming a deposit in a groove of a magnesium componenthousing, comprising the steps of: removing material from a sidewalladjacent a recessed opening of the groove to form an area, whereindamage is expected to occur in the removed material; forming a depositin the area, the deposit being integrally formed with the sidewall ofthe magnesium component and an inner surface of the recessed opening;and removing any excess material from the deposit.
 17. The methodaccording to claim 16, wherein the magnesium component is a gearboxhousing of a rotary wing aircraft.
 18. The method according to claim 16,wherein the deposit includes one or more layers of powdered materialapplied to the area through a cold spray deposition process.
 19. Themethod according to claim 18, wherein the powdered material includesaluminum.
 20. The method according to claim 16, wherein excess materialis removed so that at least one dimension of the magnesium componentincluding the deposit is substantially equal to an original dimensionthereof.